The hydrogenation of a double bond between two carbon atoms or between a carbon atom and a hetero atom is a chemical reaction which can be carried out in the presence of a catalyst. Transition metal complexes have been used as homogeneous catalysts for this reaction, but in many cases these complexes have contained phosphine ligands which tend to be expensive, unpleasant to handle and also toxic.
There have been few examples of non-phosphine ligands in catalysts for hydrogenation. Those that have been described include the following.
Frediani et al. “Quinoline transfer hydrogenation by a rhodium bipyridine catalyst”, Inorganica Chimica Acta, 359, 2650-2657 (2006) have described the use of the rhodium complex cis-[Rh(bipy)2Cl2]Cl 2H2O containing the bipyridyl ligand as a catalyst for hydrogenation.
Brunner and Agrifoglio “Hydrogenation of prochiral olefins with rhodium complexes of optically active amidines”, Monatshefte für Chemie, 111, 275-287 (1980) have disclosed olefin hydrogenation using a rhodium compound in the presence of an amidine compound. They used amidines having a general formula:
in which R1 was 1-methylbenzyl and R2 was benzyl, phenyl, isopropyl or 1-methylbenzyl.